A lever-type start switch for a user to pull is provided as part of an electric power tool such as a disc grinder etc. When the start switch is pulled (triggering an on operation, wherein hereafter on-operation refers to making a component such as the power tool operational in the ON state), an electric motor will start and the electric power tool can be used. When the start switch is released, on-operation ceases, and the electric motor will stop. The start switch is provided on a grip for a user to hold such that the switch is capable of alternating between an on-position and an off-position by tilting movement or parallel movement.
The switch has a main body which is turned on/off by an operation of the start switch. Power supply or interruption thereof to the electric motor is governed by an electric on/off signal from the switch main body. With regard to the start switch, a known problem is that malfunction may sometimes occur because, for example, an inside gap of the switch may be clogged with dust. Especially when grinding work is performed by use of a tool such as a disc grinder, peripheral portions around a support member of the start switch may also become clogged with a substantial amount of dust that is generated by the grinding work, which can consequently cause device malfunction. The malfunction of the start switch can hinder and impede a smooth start/stop operation of the device.
In order to solve the above-mentioned problems of the start switch, a technique for using a so-called electronic switch has been provided in the prior art. Within the electronic switch, a press sensor may be provided, by which a pressing operation by a user's fingertip may be detected. Alternatively a touch sensor may be provided internally in the switch wherein contact by the user's fingertip with the switch is electromagnetically detected, and in this manner there is no risk of foreign obstacles such as dust entering into the electronic switch from the outside because it is generally covered with a cover. When such an electronic switch is used as the start switch, it is necessary to take a countermeasure to prevent malfunction caused by, for example, an unintended on-operation of the start switch inadvertently by the user.
The following Patent Documents disclose techniques for accurately controlling a starting ON state of an electric power tool. Japanese Patent No. 4678199 discloses a technique for preventing the electric power tool from being stolen, such that an on-operation thereof is prohibited unless the user holds the electric power tool by transmitting and receiving information containing the right to use the electric power tool, between the electric power tool and an authentication device that the user puts on. Japanese Laid-Open Patent Publication No. 2013-188803 discloses a technique for adding an authentication feature at low cost with regard to an authentication device on a side of the electric power tool.
With regard to the start switch of the electric power tool, however, it is not only necessary to suppress theft of the electric power tool by prohibiting starting of the electric power tool while the user is not present, but it is also necessary to prevent the on-operation of the tool in an accidental or inadvertent situation by the user even if the electric power tool is not stolen. The present invention is made from this point of view and an object thereof is to allow the on-operation of the electronic switch specifically only under an intended, non-inadvertent situation for the user, where the electronic switch is used as the start switch.